The present invention relates generally to analog to digital converters, and more particularly to all optical analog to digital converters.
It is often desirable to convert an analog amplitude varying signal to a digital set of values which corresponds to various voltages in the analog waveform to generate a corresponding digital signal. Conventional approaches generally rely ion iterative and/or comparative techniques for determining a digital signal based on an analog waveform voltage. In particular, a common conventional approach compares the actual voltage of the analog amplitude varying signal to a comparison voltage which is generated from a digital word. Various digital words are utilized to create comparison voltages which are then rapidly compared to the actual voltage to determine whether the comparison voltages are greater or less than, in an instant of time, the analog amplitude varying signal. Through a continuous iterative and/or comparative process, a digital word which corresponds to the actual voltage of the analog amplitude varying signal is generated. The digital word is recorded for that instant of time and the same iterative and/or comparative process is repeated for subsequent instants of time corresponding to the analog signal. This conventional method suffers from various shortcomings, including but not limited to, errors and time inefficiency due to the iterative process.
What is needed therefore is an apparatus and method for converting an analog signal into a digital signal which is automatic, accurate, time efficient and does not rely on iterative techniques.
The preceding and other shortcomings of the prior art are addressed and overcome by the present invention which provides, in a first aspect, an apparatus for converting an analog signal into a digital signal, including a converter which converts the analog signal into an optical signal which varies in wavelength in accordance with an amplitude of the analog signal, a splitter which applies the optical signal over a preselected number of light paths, an interferometer connected to each of the light paths which applies a sinusoidal transfer function to the optical signal to generate two complimentary output signals; and, a detector connected to each of the interferometers which generates a digital bit in response to the two complimentary output signals, wherein each of the digital bits are combined to form a parallel digital word.
In another aspect, the present invention provides a method for converting an analog signal into a digital signal, including the steps of converting the analog signal into an optical signal which varies in wavelength in accordance with an amplitude of the analog signal, splitting the optical signal over a preselected number of light paths, applying a sinusoidal transfer function to the optical signal over each of the light paths to generate two complimentary output signals and generating a digital bit in response to the two complimentary output signals, wherein each of the digital bits are combined to form a parallel digital word.
The foregoing and additional features and advantages of this invention will become apparent from the detailed description and accompanying drawing figures below. In the figures and the written description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawing figures and the written description.